Snakes were learning to slither more than 167 million years ago, 70 million years earlier than pre-viously thought, fossil discoveries have shown.
The partial remains of four ancient snakes dating back to the early reign of the dinosaurs are challenging accepted theories about the creatures’ origins.
Until now, it was widely assumed that the snake’s head evolved after its elongated body. But this was based on evidence that suddenly appeared in the fossil record 100 million years ago. The new fossils point to a much older origin for snakes, and suggest that the classic snake head pre-dated a legless body.
Of the newly discovered snakes, two were from the UK. The oldest, Eophis underwoodi, was found at a site near Kirtlington, Oxfordshire. Its few fragmentary remains are thought to have come from a small individual, although it is not possible to say if the creature was a juvenile or adult when it died.
The largest snake, Portugalophis lignites, found in coal deposits near Guimarota in Portugal, measured nearly a metre or more in length.
Two other snakes, Parviraptor estesi and Diablophis gilmorei, came from Dorset and Colorado, US.
All shared recognisable features with modern-day snakes, such as sharp, backward-pointing teeth, but their body shape and size remain uncertain.
Lead scientist Michael Caldwell, from the University of Alberta, Canada, said: “The study explores the idea that evolution within the group called ‘snakes’ is much more complex than previously thought. Importantly, there is now a significant knowledge gap to be bridged by future research as no snake fossils are known from between 140 to 100 million years ago.”
The research, published in the journal Nature Communications, overturns the idea that snakes appeared suddenly and spread around the world 100 million years ago.
It suggests that from 167 million to 100 million years ago snakes were expanding globally and evolving towards their well-known body plan.
The ancient snakes occupied many different habitats, including swamps, ponds, rivers and coastal systems. Marine snakes from Lebanon and Argentina dating back 90 to 100 million years still possessed small but well-developed rear limbs.
“Based on the new evidence and through comparison to living legless lizards that are not snakes, the paper explores the novel idea that the evolution of the characteristic snake skull and its parts appeared long before snakes lost their legs,” Caldwell added.
The distribution and anatomy of the snakes makes it clear that even older snake fossils are waiting to be found.